The present invention generally relates to an apparatus and methodology for combining multiple energy storage and/or generation systems, so that a desired combination of cost and effectiveness can be achieved by efficiently switching power into, out of, and/or around the power units to supply power to a load.
There is a growing need for the electrification of the transportation industry, and to supplement the electric power generation and distribution system (the electric utility grid) by storing energy at times when the grid has excess capacity, and releasing energy into the grid at times when generation and/or grid usage approaches maximum capacity. In addition, the cost and efficiency of storing and generating electrical power to run portable appliances has become increasingly important. The system disclosed herein can provide an efficient and convenient methodology to combine multiple electrical power storage and/or generation systems (power units) so that a desired combination of cost and effectiveness can be achieved by efficiently switching power into, out of, and/or around the power units.
In the transportation vehicle industry (including watercraft) where electrical power is used, there are internal combustion engine hybrids, fuel cell hybrids, and battery electric vehicles. In the portable appliance industry, manufacturers of portable media appliances such as mobile computers, telecommunication devices, and other entertainment devices are constantly searching for an optimum mix of cost and performance in their electrical power systems. As new and different power storage and generation methodologies evolve, there may be additional modes of power for these transportation vehicles and portable appliances. The system disclosed herein can assist in finding a desired mix of existing and future energy generation and/or storage units for these industries as well as other industries facing energy generation and/or storage issues.
The utility industry is constantly searching for more efficient ways to store energy in times of excess capacity and to release energy to supplement generation at times of peak demand. In the process, various additional peak time generation units are brought online and energy storage units are discharged. The system disclosed herein can assist in combining a desired mix of energy generation and/or storage units for the utility industry and to provide backup power as well as supplemental power. This system can blend and manage multiple packs of different batteries of the same or different chemistry, with each pack having different characteristics due to state-of-life or structure, or other reason.
Different power storage and power generating units have different cost and performance characteristics. These characteristics include, but are not limited to:
Financial cost: the cost per unit of energy stored or generated;
Energy density: the weight and volume of the module versus the amount of energy stored/delivered;
Energy efficiency: the rate of storage and discharge of energy, and/or the efficiency (minimal energy loss) in storage and discharge of energy;
Cycle Life: the useful life of the module (charge, discharge and/or energy generation life), and the stability of chemistry and/or structure;
Safety: the thermal stability, chemical inertness, energy and/or chemical containment in the event of breach of containment; and
Environmental operating range: the temperature, humidity, vibration, corrosive resistance, etc.
The system disclosed herein can be used in developing a combination of power generation and/or storage units that balances these characteristics while meeting desired objectives.
The energy management system can connect a load to multiple energy sources. The energy management system includes a load connection for connecting the load; a first source connection for connecting a first energy source having a first voltage; a second source connection for connecting a second energy source having a second voltage; and a control unit for receiving communications regarding the load, the first energy source and the second energy source. The first voltage of the first energy source can be the same as or different from the second voltage of the second energy source. The energy management system transfers energy from at least one of the first energy source and the second energy source to the load when the control unit receives a power demand from the load, transfers energy from the load to at least one of the first energy source and the second energy source when the control unit receives a charging current from the load; and transfers energy from either of the first and second energy sources to the other of the first and second energy sources when the control unit determines an energy transfer is necessary.
An energy management system for coupling a load to multiple energy sources is disclosed. The energy management system includes a load connection, a first source connection, a second source connection, an inductor, four switches and a control unit. The load connection is used for connecting the load to the energy management system. The first source connection is used for connecting a first energy source having a first voltage to the energy management system. The first source connection has a positive terminal and a negative terminal, and the first source connection is in parallel with the load connection. The second source connection is used for connecting a second energy source having a second voltage to the energy management system. The second source connection has a positive terminal and a negative terminal. The second voltage can be equal to or different from the first voltage. The inductor extends from a first end to a second end. The first switch couples the positive terminal of the first source connection to the first end of the inductor. The second switch couples the negative terminal of the first source connection to the first end of the inductor. The third switch couples the positive terminal of the second source connection to the second end of the inductor. The fourth switch couples the negative terminal of the second source connection to the second end of the inductor. The control unit controls the switching of the first, second, third and fourth switches to transfer energy between the first energy source and the second energy source through the inductor.
The energy management system can also include a first diode in parallel with the first switch, a second diode in parallel with the second switch, a third diode in parallel with the third switch, and a fourth diode in parallel with the fourth switch. The energy management system can also include a first capacitor in parallel with the first source connection, and a second capacitor in parallel with the second source connection.
The energy management system can include a plurality of sensors providing readings monitoring the condition of at least one of the first energy source, the second energy source and the load. The readings can be sent to the control unit, and the control unit can use the readings to control the switching of the first, second, third and fourth switches. The energy management system can also include a sensor interface that receives and processes the sensor readings from the plurality of sensors, and then provides the processed sensor readings to the control unit. The plurality of sensors can include a first source ammeter for monitoring the current flowing through the first source, a second source ammeter for monitoring the current flowing through the second source, a load ammeter for monitoring the current flowing through the load, a first source voltmeter for monitoring the voltage across the first source, and a second source voltmeter for monitoring the voltage across the second source.
A method for controlling an energy management system that couples a system load to a first energy source and a second energy source is disclosed. The system load is connected in parallel with the first energy source, the first energy source has a positive terminal and a negative terminal, the second energy source has a positive terminal and a negative terminal. The energy management system includes an inductor extending from a first end to a second end, a first switch that couples the positive terminal of the first source to the first end of the inductor, a second switch that couples the negative terminal of the first source to the first end of the inductor, a third switch that couples the positive terminal of the second source to the second end of the inductor, and a fourth switch that couples the negative terminal of the second source to the second end of the inductor. The method for controlling the energy management system includes evaluating the states of the system load, the first energy source and the second energy source; determining the direction and proportion of energy flow between the first energy source, the second energy source and the system load; selecting whether to use a two-switch state or a one switch state to move energy between the first energy source and the second energy source; and controlling the switching of the first, second, third and fourth switches to transfer energy between the first energy source and the second energy source through the inductor using the selected one of the two-switch state or the one switch state. The two switch state closes the first and fourth switches, or the second and third switches or none of the switches at any one time. The one switch state closes only one of the switches or none of the switches at any one time.
When the energy management system also includes a first diode in parallel with the first switch, a second diode in parallel with the second switch, a third diode in parallel with the third switch, and a fourth diode in parallel with the fourth switch, the method for controlling the energy management system can also include determining, based on the direction of energy flow, which of the first energy source, the second energy source and the system load is an energy flow source and which is an energy flow destination; selecting whether to use a synchronous mode or an asynchronous mode to move energy from the energy flow source to the energy flow destination; and controlling the switching of the first, second, third and fourth switches to transfer energy from the energy flow source to the energy flow destination through the inductor using the selected one of the synchronous mode or an asynchronous mode. When the two-switch state and synchronous mode are both selected, two switches are closed to move energy from the energy flow source to the inductor and then those two switches are opened and the other two switches are closed to move energy from the inductor to the energy flow destination. When the two-switch state and asynchronous mode are both selected, two switches are closed to move energy from the energy flow source to the inductor and then those two switches are opened and energy moves from the inductor to the energy flow destination through two of the first, second, third and fourth diodes.
When the energy management system also includes a first diode in parallel with the first switch, a second diode in parallel with the second switch, a third diode in parallel with the third switch, and a fourth diode in parallel with the fourth switch, and the method for controlling the energy management system can also include determining a voltage for each of the first and second energy sources; determining, based on the direction of energy flow, which of the first energy source, the second energy source and the system load is an energy flow source and which is an energy flow destination; selecting whether to use a synchronous mode or an asynchronous mode to move energy from the energy flow source to the energy flow destination; and controlling the switching of the four switches to transfer energy from the energy flow source to the energy flow destination through the inductor using the selected one of the synchronous mode or the asynchronous mode. When the one-switch state is selected and the voltage of the energy flow source is less than the voltage of the energy flow destination, the four switches are controlled to use a boost conversion mode to transfer energy between the energy flow source and the energy flow destination through the inductor. When the one-switch state is selected and the voltage of the energy flow source is not less than the voltage of the energy flow destination, the four switches are controlled to use a buck conversion mode to transfer energy between the energy flow source and the energy flow destination through the inductor.
The method for controlling the energy management system can also include monitoring the voltage of the energy flow source and the energy flow destination; and when using the buck conversion mode and the voltage of the energy flow source becomes less than the voltage of the energy flow destination, switching from buck conversion mode to boost conversion mode.
An energy management system for coupling a load to multiple energy sources is disclosed that includes a load connection, a first source connection, a second source connection, a control unit and a plurality of energy management modules. The load connection is used for connecting the load to the energy management system. The first source connection is used for connecting a first energy source having a first voltage to the energy management system, and the second source connection is used for connecting a second energy source having a second voltage to the energy management system. The second voltage can be equal to or different from the first voltage. Each of the first and second source connections has a positive terminal and a negative terminal. The first source connection is in parallel with the load connection. Each of the plurality of energy management modules includes an inductor that extends from a first end to a second end, and four switches. The first switch couples the positive terminal of the first source connection to the first end of the inductor, the second switch couples the negative terminal of the first source connection to the first end of the inductor, the third switch couples the positive terminal of the second source connection to the second end of the inductor, and the fourth switch couples the negative terminal of the second source connection to the second end of the inductor. The control unit controls the switching of the four switches of each of the plurality of energy management modules to transfer energy between the first energy source and the second energy source through the inductor of the respective energy management module.
Each of the plurality of energy management modules can also include a first diode in parallel with the first switch, a second diode in parallel with the second switch, a third diode in parallel with the third switch, and a fourth diode in parallel with the fourth switch. The energy management system can also include a first capacitor in parallel with the first source connection, and a second capacitor in parallel with the second source connection. The energy management system can also include a plurality of sensors providing readings monitoring the condition of at least one of the first energy source, the second energy source and the load, where the readings are sent to the control unit which uses them to control the switching of the four switches of each of the plurality of energy management modules. The energy management system can also include a sensor interface that receives and processes the sensor readings from the plurality of sensors, and provides the processed sensor readings to the control unit. The plurality of sensors can include one or more of a first source ammeter for monitoring the current flowing through the first source, a second source ammeter for monitoring the current flowing through the second source, a load ammeter for monitoring the current flowing through the load, a first source voltmeter for monitoring the voltage across the first source, and a second source voltmeter for monitoring the voltage across the second source.
The energy management system can also include a third source connection for connecting a third energy source to the energy management system, and at least one supplementary energy management module. The third source connection has a positive terminal and a negative terminal. Each of the at least one supplementary energy management modules includes an inductor extending from a first end to a second end and four switches. The first switch couples the positive terminal of the first source connection to the first end of the inductor, the second switch couples the negative terminal of the first source connection to the first end of the inductor, the third switch couples the positive terminal of the third source connection to the second end of the inductor, and the fourth switch couples the negative terminal of the third source connection to the second end of the inductor. The control unit also controls the switching of the four switches of each of the at least one supplementary energy management modules to transfer energy between the first energy source and the third energy source through the inductor of the respective supplementary energy management module. Each of the at least one supplementary energy management modules can include a first diode in parallel with the first switch, a second diode in parallel with the second switch, a third diode in parallel with the third switch, and a fourth diode in parallel with the fourth switch. The energy management system can also include a third capacitor in parallel with the third source connection. The energy management system can include a plurality of sensors providing readings monitoring the condition of at least one of the first, second and third energy sources and the load. The readings can be sent to the control unit which uses the readings to control the switching of the four switches of each of the plurality of energy management modules and of each of the at least one supplementary energy management modules. The plurality of sensors can include a first source ammeter for monitoring the current flowing through the first source, a second source ammeter for monitoring the current flowing through the second source, a third source ammeter for monitoring the current flowing through the third source, a load ammeter for monitoring the current flowing through the load, a first source voltmeter for monitoring the voltage across the first source, a second source voltmeter for monitoring the voltage across the second source, and a third source voltmeter for monitoring the voltage across the third source.
The energy management system can also include a communications bus connecting the control unit to each of the plurality of energy management modules. The control unit can send commands to each of the plurality of energy management modules through the communications bus. The control unit can receive status information from each of the plurality of energy management modules through the communications bus, and the control unit can use the status information to apportion the amount of energy transferred by each of the plurality of energy management modules. The energy management system can include a user input module for receiving user commands, and the control unit can use the user commands to control the switching of the four switches of each of the plurality of energy management modules. The energy management system can include a user output module for displaying status of the energy management system.
The energy management system can include a redundant control unit that monitors the health of the control unit. When the redundant control unit determines that the control unit is not functioning properly, the redundant control unit can control the switching of the switches of each of the plurality of energy management modules to transfer energy between the first energy source and the second energy source through the inductor of the respective energy management module. At least one of the plurality of energy management modules can be a protected energy management module that also includes protection logic to protect itself from damage. The protected energy management module takes into account the status of the protection logic when responding to commands from the control unit.
A method for controlling an energy management system that couples a system load to a first energy source and a second energy source is disclosed that uses a plurality of energy management modules. The system load is connected in parallel with the first energy source, and the first and second energy sources have a positive terminal and a negative terminal. Each of the plurality of energy management modules includes an inductor extending from a first end to a second end and four switches. The first switch couples the positive terminal of the first source connection to the first end of the inductor, the second switch couples the negative terminal of the first source connection to the first end of the inductor, the third switch couples the positive terminal of the second source connection to the second end of the inductor, and the fourth switch couples the negative terminal of the second source connection to the second end of the inductor. The method for controlling the energy management system includes evaluating the conditions of the system load, the first energy source and the second energy source; determining whether to control the energy management system using manual mode or automatic mode; and controlling the switching of the four switches of each of the plurality of energy management modules to transfer energy between the first energy source and the second energy source through the respective inductor.
The method for controlling the energy management system in manual mode can include receiving user input parameters defining the direction and proportion of energy flow between the first energy source, the second energy source and the system load; and controlling the switching of the four switches of each of the plurality of energy management modules to transfer energy in accordance with the user input parameters. The method for controlling the energy management system in manual mode can also include determining, based on the direction of energy flow, which of the first energy source, the second energy source and the system load is an energy flow source and which is an energy flow destination; apportioning the energy flow between each of the plurality of energy management modules in accordance with the user input parameters; for each of the plurality of energy management modules, selecting whether to use a two-switch state or a one switch state to move the apportioned amount of energy from the energy flow source to the energy flow destination; for each of the plurality of energy management modules, selecting whether to use a synchronous mode or an asynchronous mode to move the apportioned amount of energy from the energy flow source to the energy flow destination; and controlling the switching of the four switches of each of the plurality of energy management modules to transfer energy from the energy flow source to the energy flow destination through the respective inductor using the selected one of the two-switch state or the one switch state, and of the synchronous mode or the asynchronous mode.
The method for controlling the energy management system in automatic mode can include determining the direction and proportion of energy flow between the first energy source and the second energy source and the system load; determining, based on the direction of energy flow, which of the first energy source, the second energy source and the system load is an energy flow source and which is an energy flow destination; apportioning the energy flow between each of the plurality of energy management modules; for each of the plurality of energy management modules, selecting whether to use a two-switch state or a one switch state to move the apportioned amount of energy from the energy flow source to the energy flow destination; for each of the plurality of energy management modules, selecting whether to use a synchronous mode or an asynchronous mode to move the apportioned amount of energy from the energy flow source to the energy flow destination; and controlling the switching of the four switches of each of the plurality of energy management modules to transfer energy from the energy flow source to the energy flow destination through the respective inductor using the selected one of the two-switch state or the one switch state, and of the synchronous mode or the asynchronous mode. The two switch state closes either the first and fourth switches, the second and third switches or none of the switches at any one time; and the one switch state closes only one of the switches or none of the switches at any one time.
Determining the direction and proportion of energy flow between the first energy source and the second energy source and the system load can include determining whether the system load is using energy from the first and second energy sources; determining whether the system load is supplying energy to the first and second energy sources; and, when the system load is neither using nor supplying energy, determining whether to perform energy balancing between the first and second energy sources. When it is determined that the system load is using energy from the first and second energy sources, the method for controlling the energy management system can include determining whether the amount of current to be supplied to the system load is greater than a threshold current, determining whether at least one of a voltage of the first energy source is less than a threshold voltage and a state-of-charge of the first energy source is less than a threshold state-of-charge, and apportioning the energy flow from the first and second energy sources to the system load accordingly; and when none of the thresholds are exceeded, comparing a timer to a timeout value. When it is determined that the system load is supplying energy to the first and second energy sources, the method for controlling the energy management system can include determining whether the amount of current to be supplied by the system load is greater than a threshold current, determining whether at least one of a voltage of the first energy source is greater than a threshold voltage and a state-of-charge of the first energy source is greater than a threshold state-of-charge, and apportioning the energy flow from the system load to the first and second energy sources accordingly; and when none of the thresholds are exceeded, comparing a timer to a timeout value. When it is determined to perform energy balancing between the first and second energy sources, the method for controlling the energy management system can include determining a state-of-charge of the first and second energy sources, comparing the state-of-charge of the first energy source to maximum and minimum state-of-charge values; comparing the state-of-charge of the second energy source to maximum and minimum state-of-charge values; and apportioning the energy flow between the first energy source and the second energy sources based on the comparisons with the maximum and minimum state-of-charge values.
The method for controlling the energy management system can include selecting N of the plurality of energy management modules to transfer energy between the first energy source and the second energy source, and synchronizing the switching of each of the N selected energy management modules to be out of phase and interlaced with each other. If the time period for the switching of all of the energy management modules is T_sw, then controlling each energy management module to transfer energy for a period of T_sw/N, and offsetting the start time of each successive energy management module by T_sw/N. In this manner, the first energy management module starts conducting energy at time 0, then the first energy management module stops conducting and the second energy management module starts conducting at time T_sw/N, and so on until the (N−1)th energy management module stops conducting and the Nth energy management module starts conducting at time (N−1)*T_sw/N, and the Nth energy management module stops conducting at time T_sw/N, which may be time 0 for the next cycle.
The method for controlling the energy management system can include detecting each of the plurality of energy management modules controlled by the energy management system. The method for controlling the energy management system can include receiving sensor readings indicating the condition of the system load, the first energy source and the second energy source; using the sensor readings to evaluate the condition of the system load, the first energy source and the second energy source; and monitoring the sensor readings while controlling the switching of the first, second, third and fourth switches of each of the plurality of energy management modules.
For a more complete understanding of the present disclosure, reference is now made to the following detailed description and the accompanying drawings.